An air traffic control system outage at Amsterdam’s Schiphol Airport and strikes across Italy are disrupting air travel in Europe ahead of a busy Thanksgiving travel weekend.

According to a statement on KLM – Royal Dutch Airlines’ website, a technical failure in the air traffic control system at Schiphol Airport caused major travel disruptions late Tuesday, local time, and passengers flying through the airport may still experience problems. KLM customers with tickets issued on or before November 21 can change their travel dates through Tuesday, November 28, in the same travel class without paying a change fee. Customers can also use the full value of their original tickets for tickets to a new destination without paying a change fee. If their flight was canceled or delayed more than three hours and they did not travel, customers can apply for a full refund. Customers can check their current flight status here.

The airline told The Sun that the disruption resulted in the cancellation of 50 flights, including roundtrip flights to London Heathrow, Paris, Nantes and Hanover.